International Association
for Cryptologic Research

In this work, we generalize threshold Schnorr signatures, ElGamal encryption, and a wide variety of other functionalities, using a novel formalism of group reconstruction circuits (GRC)s. We construct a UC secure MPC protocol for computing these circuits on secret shared inputs, even in the presence of malicious parties. Applied to concrete circuits, our protocol yields threshold signature and encryption schemes with similar round complexity and concrete efficiency to functionality-specific protocols. Our formalism also generalizes to other functionalities, such as polynomial commitments and openings.